Excluding fields from results in MongoDB - Mini Project: Build & Apply

Excluding Fields from MongoDB Query Results

📖 Scenario: You are managing a small online bookstore database. You want to retrieve information about books but exclude some details like the internal _id field and the supplier information from the results to keep the output clean and focused.

🎯 Goal: Build a MongoDB query that fetches all books but excludes the _id and supplier fields from the returned documents.

📋 What You'll Learn

Create a collection named books with given book documents

Add a query filter variable to select all books

Write a MongoDB find query that excludes the _id and supplier fields

Complete the query with the correct projection to exclude fields

💡 Why This Matters

🌍 Real World

Excluding fields from query results helps keep data clean and protects sensitive information when sharing or displaying data.

💼 Career

Database developers and data analysts often need to control which fields are returned in queries to optimize performance and maintain privacy.

1

Create the books collection with sample documents

Create a variable called books that holds an array of three book documents with these exact fields and values: { title: "The Great Gatsby", author: "F. Scott Fitzgerald", year: 1925, supplier: "SupplierA" }, { title: "1984", author: "George Orwell", year: 1949, supplier: "SupplierB" }, and { title: "To Kill a Mockingbird", author: "Harper Lee", year: 1960, supplier: "SupplierC" }.

MongoDB

# Your code here

Need a hint?

Use an array of objects with exact field names and values.

2

Create a query filter to select all books

Create a variable called query and set it to an empty object {} to select all documents in the books collection.

MongoDB

const books = [
  { title: "The Great Gatsby", author: "F. Scott Fitzgerald", year: 1925, supplier: "SupplierA" },
  { title: "1984", author: "George Orwell", year: 1949, supplier: "SupplierB" },
  { title: "To Kill a Mockingbird", author: "Harper Lee", year: 1960, supplier: "SupplierC" }
];

# Your code here

Need a hint?

Use an empty object {} to select all documents.

3

Write a find query excluding _id and supplier fields

Create a variable called projection and set it to an object that excludes the _id and supplier fields by setting them to 0. Then create a variable called result that simulates the MongoDB find method by filtering books with query and mapping to exclude the specified fields using projection.

MongoDB

const books = [
  { title: "The Great Gatsby", author: "F. Scott Fitzgerald", year: 1925, supplier: "SupplierA" },
  { title: "1984", author: "George Orwell", year: 1949, supplier: "SupplierB" },
  { title: "To Kill a Mockingbird", author: "Harper Lee", year: 1960, supplier: "SupplierC" }
];

const query = {};

# Your code here

Need a hint?

Set fields to 0 in projection to exclude them. Use map to remove those fields from each book.

4

Complete the query with the correct projection

Add a comment above the result variable that says // Query result excluding _id and supplier fields to clearly label the final output.

MongoDB

const books = [
  { title: "The Great Gatsby", author: "F. Scott Fitzgerald", year: 1925, supplier: "SupplierA" },
  { title: "1984", author: "George Orwell", year: 1949, supplier: "SupplierB" },
  { title: "To Kill a Mockingbird", author: "Harper Lee", year: 1960, supplier: "SupplierC" }
];

const query = {};

const projection = { _id: 0, supplier: 0 };

# Your code here
const result = books.map(({ _id, supplier, ...rest }) => rest);

Need a hint?

Add a comment to label the final query result clearly.